In production lines of solar cells and solar modules, it is desired to measure characteristics of these solar cells and modules at a high rate of speed in order to have a high production throughput. Generally, the solar cells (or modules) are measured under an illumination at an intensity of one sun. One sun is approximately 100 mW/cm2 of light intensity, having a light spectrum similar to sunlight.
One issue that limits the speed at which accurate tests can be made is the time response of the solar cell. For example, if you measure short circuit current (i.e., when the cell voltage is 0V) and then switch to open-circuit voltage with a typical measurement apparatus, it takes time for the solar cell to increase its voltage (when a light pulse is applied) up to the steady-state voltage after the open-circuit voltage condition is commanded by the control circuitry. Because measurements of characteristics of a solar cell are typically taken at different voltages (e.g., short circuit, maximum power conditions, open-circuit, etc.), and because it takes time for the solar cell to ramp up to these voltages, current measurement techniques can be relatively time-consuming and slow down a production line. Measurements may be performed as disclosed in U.S. Pat. Nos. 7,309,850 and 7,696,461 which are both incorporated by reference.
Accordingly, new techniques are desirable that would speed up the measurement of various characteristics of solar cells and solar modules.